Back injury

A year ago my partner had a multi-level laminectomy to remove an abyss in his lower disc area.
Not long after or at the time of the operation, we are not sure, one of his discs fully obliterated.
Since this operation my partner has suffered daily in various ways.
Anything can upset his back; movement, standing too long, walking too long, sitting in certain positions and for too long / including in the car, laying certain ways or for too long, walking on uneven ground, sitting to go to the loo, bending down and it goes on. He is on painkillers daily.
He is unable to do any recreational activites, he has only been able to for eg, come for a drive to the local shopping centre to pick up some groceries / though he isn't able to pick up heavy groceries or push the trolley and just other short errands like picking the kids up from school down the road etc.
He hasn't been able to resume any of his pre-op recreational activities. For example he used to go boat fishing but knows that this would not be ideal even with assistance.
He has had leg and buttock pain on and off since the operation, even though the surgeon said that the nerves were clear.
The surgeon he saw for a second opinion said that it is understandable that he would have toileting problems as some of the organs were crushed. This explains why he has problems with spontaneous diahorea at times and also regulary throws up. But we are not sure why his local GP isn't totally convinced that these regular symptoms are fully connected?
My partner has been attending physio and hydrotherapy as much as possible, usually on a weekly basis and he is starting to see a phsychologist due to his depression.
The two surgeons that my partner saw both said to wait a year then to return for a spinal fusion to relieve the pain.
Disc replacement was out of the question because the disc wouldn't last for the rest of his life.
My main questions are that with other damaged discs surrounding this obliterated disc is spinal fusion a good path to take? Does anyone just live their life with a disc missing and be expected to be okay on a day to day basis / is this normal to just leave nothing in the disc space if fusion may cause further complications?